A caption can make an image more useful by explaining what is known and where that knowledge comes from. It can also create false certainty when an attractive guess is presented as a fact. Small choices of wording matter.
Begin with the strongest supported information. If a person or place has been identified through a named source, make that connection clear in your working notes. When an identification remains tentative, let the published caption reflect that uncertainty.
Avoid asking one image to prove more than it shows. A photograph may support an observation about a visible detail while leaving the surrounding event unexplained. Additional context belongs beside the image only when it has its own support.
Clearly label conceptual or generated illustrations as such. They can accompany a discussion of research without becoming historical evidence. A good caption helps the reader understand both the purpose of the visual and the boundaries of what it can establish.